1. Field of the Invention
The invention herein relates to a direct manufacturing method of hydrogen peroxide in aqueous solution, wherein transition metals in Group VIII including palladium or platinum, and organic compounds such as alkyl anthraquinone, anthraquinone-2-carbonylic acid or the like, 1,2-diphenylhydrdzine and azobenzene are encapsulated onto the zeolite channels, and then reducing agents such as hydrogen, ammonia or hydrogen sulfide in addition to oxygen are simultaneously supplied therein in a range of 10.about.90.degree. C. and at an atmosphere.
2. Description of the Prior Art
Based on the continuous research and development of the manufacturing method of hydrogen peroxide, a mass production of hydrogen peroxide is now possible. Almost every sector of the industry is utilizing hydrogen peroxide, and the trend is that its application will be expanded even more. The usefulness of hydrogen peroxide is based mainly on its oxidation property though it is also used in substitution and degradation reactions. As for the application range of hydrogen peroxide, one of the most applicable area is its use as bleacher. Hydrogen peroxide is degraded into water after use, and in this regard, there is no pollution problem. Due to its environmentally-friendly characteristics, the trend is that its use in the fields of water treatment, chemical industry and environment protection sector will increase. In particular, if hydrogen peroxide is used in waste water treatment, there is an advantage in that BOD, COD, color and order can be effectively reduced. It is also used in expoxidation, hydroxylation, oxidation, and initialization of polymerization in addition to its role as supplier of oxygen in a variety of organic chemical industrial sectors.
Hydrogen peroxide has been commercially manufactured by means of the Riedl-Pfeiderer process or AO process which were developed during the late 1940's to early 1950's. AO process consists of two-step processes in which the first step comprises a conversion process of alkyl anthraquinone into alkyl anthrahydroquinone. The second step comprises a process of oxidation of alkyl hydroquinone by oxygen for the purpose of manufacturing hydrogen peroxide. In the AO process, within a carrier solvent commonly called a working solution, alkylanthraquinone and alkyl anthrahydroquinone alternately become reduced and oxidized, thereby producing hydrogen peroxide.
Based on the research into the topic of the manufacture of hydrogen peroxide the effects of the type of anthraquinones, the composition of and change in a working solution, type of catalysts, and quinone compounds on the manufacture of hydrogen peroxide have been duly disclosed. The catalyst used in the manufacturing process is prepared by impregnating palladium or nickel into a stable carrier, and hydrogen peroxide is extracted by using water. Consequently, hydrogen peroxide in solution always contains organic solvents as impurities, which in return requires a further refining process. Furthermore, the disadvantage of the AO process lies in the complicated and expensive manufacturing process wherein the loss of alkyl anithraquinone is caused by deterioration in the activity of the hydrolyzed catalyst. As such, the non-homogeneous catalyst which can be used in solution for the purpose of producing hydrogen peroxide is deemed necessary.
The method of directly manufacturing hydrogen peroxide from hydrogen and oxygen has been tried, without the use of organic solvents which had been used as working solution due to its favorable environmental and economical considerations. While the conventional production method of hydrogen peroxide uses a homogeneous catalyst in working solution, the direct method is characterized by the use of a non-homogeneous catalyst in aqueous solution. The method of manufacturing hydrogen peroxide by means of using hydrogen and oxygen under the non-homogeneous catalyst has been reported in U.S. Pat. No. 4,899,705 (1989) and U.S. Pat. No. 5,135,731 (1992). In U.S. Pat. No. 4,227,458, granted to Du Pont of USA as assignee, after impregnating palladium into a carbon carrier, hydrogen at atmospheric pressure of 25 and oxygen at atmospheric pressure of 140 were infused into a pressurized reactor in an acidic condition by means of reaction promotors such as bromine and chorine compounds, and then the reaction therein was carried out for 3 hours at room temperature. At that point, the concentration of hydrogen peroxide so prepared was 12.6 wgt %, and the selectivity for hydrogen peroxide was 66%. The non-homogeneous catalyst for directly manufacturing hydrogen peroxide from hydrogen and oxygen was prepared by means of impregnating a transitional metal in Group VIII into a stable supports.
However, in the manufacturing process of hydrogen peroxide at an industrially usable concentration, there is a danger with respect to handling hydrogen and oxygen since they must be injected at high pressure. Therefore, the aforementioned process has yet to be commercialized. In order to commercialize the aforementioned manufacturing method of hydrogen peroxide, several key problematic points must be solved: i.e., low concentration of manufactured hydrogen peroxide, low selectivity for hydrogen peroxide with respect to consumed hydrogen, slow reaction rate and oxygen-only reaction condition. Furthers the characteristic of the aforementioned process is that hydrogen peroxide is manufactured in an acidic aqueous medium.
U.S. Pat. No. 4,009,252 granted to Izu et al. discloses a method of producing hydrogen peroxide in the amount of 9-12 wgt % in acidic environment (1 g of hydrochloric acid, 49 g of sulfuric acid) by using a catalyst in which palladium has been precipitated in silicic acid. There, the mole ratio between oxygen and hydrogen injected into the reaction was 1.5.about.20, and the selectivity af hydrogen peroxide with respect to hydrogen was relatively high at 80.about.89%. The reaction rate was rather slow at 1 or less. From the process, 6 g of hydrogen peroxide was produced per 1 liter of aqueous solution. In U.S. Pat. No. 4,772,458 granted to Gosser et al., hydrogen peroxide at a high concentration and reaction rate was obtained in a low acidic condition by using a catalyst in which the metals were impregnated into a variety of carriers although the process was deemed quite dangerous. When a bromide ion was used in the reaction, the selectivity was 30-70%. When a chloride ion was used, the selectivity was low at 6%. When the ratio of 1/10 was used for platinum to palladium in the alumina carrier during the manufacture of hydrogen peroxide, the concentration of hydrogen peroxide was 17.8%. In U.S. Pat. No. 5,374,339 granted to Guillet and Friedman discloses a method of manufacturing hydrogen peroxide by means of impregnating anthraquinone onto an undissolved solid. The catalyst used a hydrogen transfer organic substance such as alcohol to reduce the impregnated anthraquinone. Then, hydrogen peroxide was produced when the oxidation reaction by oxygen was carried out. There, the reaction was a light reaction based on light, and anthraquinone was recycled into the original form after oxidation therein.
Further, U.S. Pat. No. 5,480,629 granted to Thompson et al. teaches a method of manufacturing hydrogen peroxide via light in the presence of hydrogen and oxygen by means of using lamellar compounds which have been encapsulated with chelated metals. During the manufacturing of hydrogen peroxide, the ends of the lamellar compounds which were encapsulated with the chelated metals consist of phosphate and arsenate. These end portions were divalent electron receptors. The lamellar portions were divided by a vertical alignment layer of IV.sub.A, IV.sub.B, III.sub.A and III.sub.B, and the non-valent transitional metals in Group VIII were encapsulated into the chelated layer. The aforementioned chelated substance is a catalyst for manufacturing hydroden peroxide from hydrogen and oxygen and is very useful for converting and storing solar energy.
Based on the metals which are impregnated into the catalyst or hydrogen carrier, the hydrogen peroxide so produced can be compared in terms of turnover frequency. The turnover frequency as below is a turnover number of hydrogen peroxide produced from 1 liter of solution during 1 hour by a catalyst based oil transitional metals or hydrogen carriers in 1 g of a catalyst. According to the recently reported journal by Thomson (J. Catal., 161, 62 (1996)), the turnover frequency with respect to hydrogen peroxide was disclosed as 13. There, the oxygen injected as a static condition had atmospheric pressure of 1, and oxygen had atmospheric pressure of 7. after which the reaction was carried out for 1 hour. In the aforementioned U.S. Pat. No. 4,009,525, hydrogen with atmospheric pressure of 0.29 and oxygen with 0.71 atmospheric pressure were injected as a static condition for reaction in order to produce hydrogen peroxide. There, the turnover frequency of palladium with respect to hydrogen peroxide as calculated was determined to be 4,400, which suggests a is relatively high activity. However, in U.S. Pat. No. 4,279,883, in which hydrogen peroxide is manufactured by means of injecting continual pressurized hydrogen and oxygen, the turnover frequency of palladium was 22, which was lower than that in the manufacturing method hydrogen peroxide in a static condition. The low turnover frequency of palladium was also observed in U.S. Pat. No. 4,335,092 granted to Air Product as assignee, in which a reaction was carried out by continuously injecting hydrogen and oxygen.
The methods for encapsulating organic compounds into the zcolite pores include flexible ligand route, template synthesis route and zeolite synthesis route. In the flexible liganid route method, chelated metals are first ion-exchanged, and the chelated metals larger than the size of the zeolite pores are encapsulated by means of expanding relatively flexible ligands. In the template synthesis route, the chelated metals smaller than the size of the zeolite pores are encapsulated by means of expanding the ligands into the pores in order to substitute the ligands with those already in place. The zeolite synthesis route is a method of encapsulating by adding chelated metals during the synthesis of zeolite. In the invention herein, the catalyst was manufactured by application of the flexible ligand route method.
The measurement methods of the hydrogen peroxide concentration include various titration methods such as a KMnO.sub.4 method, cerium method and iodometry a gasometric method which measures the amount of oxygen gas generated when H.sub.2 O.sub.2 is distributed, and a calorimetric method using a spectrocolorimeter. Among these methods, the most widely used and accurate method is a titration method using the reduction and oxidation reactions of hydrogen peroxide. In particular, the KMnO.sub.4 method and cerium methods are mainly used. In the KMnO.sub.4 method, the concentration of hydrogen peroxide can be most accurately measured given that the inorganic or organic substances which react with hydrogen peroxide ions are absent. The cerium method can be used instead of the KMnO.sub.4 method when organic or chloride substances are present which can react with MnO.sub.4. In the present invention, the KMnO.sub.4 method was used to measure the amount of hydrogen peroxide since organic or chloride substances do not exist in the reaction system.